1488, 75188 TTL to RS232 level shifter. The outputs are at RS-232 levels, and sometimes are connected to ground through a small capacitor (up to 470 pF) to reduce slew-rate. Note that 1B is missing (and can be taken to be 1 at all times). Usually VDD=+12 and VEE=-12. +----------+ +-------------+ VEE |1 +--+ 14| VDD | A | B | Y | 1A |2 13| 4A |---+---+-----| 1Y |3 12| 4B | 0 | 0 | VDD | 2A |4 1488 11| 4Y | 0 | 1 | VDD | 2B |5 10| 3A | 1 | 0 | VDD | 2Y |6 9| 3B | 1 | 1 | VEE | GND |7 8| 3Y +-------------+ +----------+ [This information is part of the GIICM]